Tuning fork type crystal component for angular velocity sensor and manufacturing method thereof

ABSTRACT

The present invention provides an angular velocity sensor element that can be produced easily with a high degree of accuracy, and a manufacturing method thereof. In the angular velocity sensor element of the present invention, the lengthwise direction of a tuning fork shaped crystal element is a Y axis of a crystal axis, the widthwise direction is an X axis and the depthwise direction is a Z axis, and mutually electrically separated first and second sensor electrodes for angular velocity detection are provided on at least one face among side faces of the tuning fork arm. The tuning fork shaped crystal element is formed from a single crystal wafer by a photo-etching technique, and the side face of the tuning fork arm on which the first and second sensor electrodes are formed is a +X face of the crystal, and the first and second sensor electrodes are arranged on both sides of a protrusion ridge line section on the +X face that occurs in the lengthwise direction of the side face due to crystallinity of the crystal.

BACKGROUND OF THE INVENTION

The present invention relates to a tuning fork type crystal componentfor an angular velocity sensor (hereinafter referred to as an “angularvelocity sensor element”) and a manufacturing method thereof, and inparticular, to a sensor electrode of the angular velocity sensorelement.

Angular velocity sensor elements are generally known which detectelectric charge generated in an arm of a tuning fork by so-calledCoriolis force when the tuning fork is vibrating. Moreover, angularvelocity sensor elements are used for example in vehicle guidancesystems, and devices for preventing camera shake, and mass productionthereof is advancing.

FIGS. 6A and 6B are drawings describing a conventional example of anangular velocity sensor element, FIG. 6A showing an angular sensorelement, and FIG. 6B showing a connection drawing thereof.

As shown in FIG. 6A, this angular velocity sensor element comprises aZ-cut tuning fork shaped crystal element 10 having a pair of tuning forkarms 1 a and 1 b that extend from a tuning fork base portion 2. Drivingelectrodes 3 a, 3 b, and 4 a, 4 b, which excite tuning fork vibration,are formed on both principal planes and on the inside and outside sidefaces of one tuning fork arm 1 a respectively. The driving electrodes 3a and 3 b on the both principal planes and the driving electrodes 4 aand 4 b on the inside and outside side faces are commonly connected viarespective wiring patterns (not shown in the drawing). In thisconventional example, the driving electrodes of the inside and outsideside faces are made a reference potential.

Moreover, a pair of sensor electrodes that detect electric charge causedby the Coriolis force, are formed on the inside and outside side facesof the other tuning fork arm 1 b. As shown in FIG. 6A and FIG. 6B, thepair of sensor electrodes comprises a ground electrode 5 on the insideside face, and electrically separated first and second sensor electrodes6 a and 6 b provided on left and right sides of the outside side face.Furthermore, an electric charge generated with inverse sign to theground electrode 5 in the tuning fork arm 1 b, by the bending thatoccurs in the orthogonal direction to the plate face (principal plane ofthe tuning fork shaped crystal element 10) due to the Coriolis force, isdetected by the first and second sensor electrodes 6 a and 6 b.

In particular for the first and second sensor electrodes 6 a and 6 bwhich are provided on the outside side face, the area and position needto be formed with a required degree of accuracy. If accuracy of these isnot maintained, this can cause a deterioration in uniformity of angularvelocity detection sensitivity for the target object, and may also causegeneration of unnecessary signals other than the signal originating fromthe angular velocity.

Also, monitor electrodes 7 a and 7 b are formed on both principal planesof the other tuning fork arm 1 b, for detecting the electric charge dueto the amplitude of the tuning fork vibration, to control the amplitudeof the tuning fork vibration. In FIG. 6B, reference symbols D1 and D2denote drive terminals, reference symbols S1 and S2 denote sensorterminals, and reference symbols M1 and M2 denote monitor terminals.

The electrodes are formed for example by setting a mechanicallyprocessed individual tuning fork shaped crystal element 10 in a platingframe (not shown in the drawing), and placing this in a vapor depositionapparatus, and then depositing a metallic film on the required places ofthe crystal element 10. Alternatively, a number of fork shaped crystalelements 10 are integrally formed on a single crystal wafer using aphoto-etching technique.

This photo-etching technique generally comprises a photolithographytechnique (photo-print technique) and a wet etching technique. Forexample, when forming the tuning fork shaped crystal element 10, atuning fork shaped hydrofluoric acid resisting mask is formed on thesingle crystal wafer, and it is immersed in hydrofluoric acid typeetchant to remove unwanted parts. Also, when forming the electrodes, apositive or negative photo-resist film (hereinafter referred to as“resist film”) is applied on the metallic film provided on the tuningfork shaped crystal element 10, and selective exposure and developmentare performed, after which unwanted parts of the metallic film areremoved by etching to form each electrode pattern (photolithographytechnique).

However, in the conventional angular velocity sensor element constructedas described above, forming the electrodes with a plating frame and bydeposition depends on mechanical accuracy of the plating frame itselfand the framing operation. As a result, naturally there has been alimitation for forming electrodes with a high degree of accuracy, forboth principal planes and each side face, particularly including thefirst and second sensor electrodes 6 a and 6 b on the outside side faceof the other tuning fork arm 1 b. When miniaturization of the element isattempted, this problem becomes greater.

Also, when forming the first and second sensor electrodes 6 a and 6 b onthe side face of the tuning fork shaped crystal element 10 using aphoto-etching technique, a formation method may be performed in which asingle crystal wafer on which the tuning fork shaped crystal element 10is already formed is exposed from an oblique direction. However, whenthis method is employed, the exposure equipment becomes larger, andthere is an issue in that technical problems and may arise due to theoblique exposure.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an angular velocitysensor element that can be produced easily with a high degree ofaccuracy, and a manufacturing method thereof.

The present invention focuses attention on a peak shaped protrusion thatnaturally occurs on a side face corresponding to a +X face of a tuningfork shaped crystal element (tuning fork arm) by etching, due to theetching anisotropy of the crystal, and actively utilizes this peakshaped protrusion to form the first and second sensor electrodes.

The angular velocity sensor element of the present invention is a tuningfork type crystal component for an angular velocity sensor comprising: atuning fork shaped crystal element having a pair of tuning fork armsextending from a tuning fork base portion where an X axis of a crystalaxis (XYZ) is a widthwise direction, a Y axis is a lengthwise directionand a depthwise direction is a Z axis; and mutually electricallyseparated first and second sensor electrodes for angular velocitydetection formed on at least one face among side faces of the tuningfork arms, wherein the tuning fork shaped crystal element is formed by aphoto-etching technique, and the first and second sensor electrodes area +X face among the side faces of the tuning fork arms, and are arrangedon both sides of a protrusion ridge line section that occurs in alengthwise direction of the +X face. Specifically, the construction issuch that a division region of the first and second sensor electrodes isprovided on the protrusion ridge line portion, and the first and secondsensor electrodes are arranged on both sides thereof.

Moreover, a manufacturing method of an angular velocity sensor elementaccording to the present invention is a manufacturing method of a tuningfork type crystal component for an angular velocity sensor comprising: atuning fork shaped crystal element having a pair of tuning fork armsextending from a tuning fork base portion where an X axis of a crystalaxis (XYZ) is a widthwise direction, a Y axis is a lengthwise directionand a depthwise direction is a Z axis; and mutually electricallyseparated first and second sensor electrodes for angular velocitydetection formed on at least one face among side faces of said tuningfork arms; wherein the manufacturing method comprises: an outlineprocessing step for forming on a single crystal wafer by a photo-etchingtechnique a number of the tuning fork shaped crystal elements havingprotrusion ridge line sections that have remained in the lengthwisedirection of +X faces of the crystal after etching, due to etchinganisotropy; an electrode material formation step for forming a metallicfilm on each side face, including both principal planes and the +X faceof the tuning fork shaped crystal element of the single crystal wafer;and an electrode dividing step for dividing the metallic film of the +Xface along the protrusion ridge line section, and forming the first andsecond sensor electrodes.

In the angular velocity sensor element of the present invention, thefirst and second sensor electrodes are formed on both sides of theprotrusion ridge line section that occurs on the +X face among the sidefaces of the tuning fork shaped crystal element (tuning fork arm). As aresult, after the metallic film is formed on the entire side face (+Xface) of the tuning fork shaped crystal element, the first and secondsensor electrodes can be easily obtained if the metallic film section onthe protrusion ridge line section is removed and divided byphoto-etching, or a laser technique and the like.

In this case, the side face corresponding to the +X face of the tuningfork is an inclined surface towards the protrusion ridge line from theprincipal plane of the tuning fork. That is, when viewing the tuningfork wafer from the top face, this inclined surface and the protrusioncan be seen. Therefore, in either case of carrying out division using aphoto-etching technique or using a laser technique (irradiation),exposure or laser irradiation to the single crystal wafer can be donefrom the perpendicular direction, so that an increase in the size andcomplexity of the equipment used can be avoided.

Here, when only side face division is performed, this objective can beachieved even if exposure or laser irradiation is performed from oneprincipal plane of the wafer. In this case, the man-hours can beshortened and the equipment simplified. Of course, exposure or laserirradiation may be performed from both faces of the wafer. This case ispreferable since a division line centering on the protrusion ridge linepart can be formed. Also, the exposure area and laser irradiation arearatio of the front side and the back side of the wafer may be adjustedwith the protrusion ridge line portion as the border. Thus, it becomespossible to adjust unnecessary output and the like.

Moreover, since the formation of the electrodes in the present inventionbasically employs a photo-etching technique (photolithography), theposition and area of the electrodes formed on the principal planes andthe side faces, including the first and second sensor electrodes, can becontrolled with a high degree of accuracy. Although there is a similaradvantage in the case of using laser irradiation, particularly in thecase of using the photo-etching technique, the advantage is evengreater.

Furthermore, concomitantly, since both sides of the protrusion ridgeline section on which the first and second sensor electrodes are formedare inclined faces, the electrode area can be made greater and detectionsensitivity can be improved compared to the case of a horizontalsurface. These effects become more significant as miniaturization of thecrystal oscillator progresses.

A manufacturing method of the angular velocity sensor element of thepresent invention comprises: the steps of an outline processing forforming on the single crystal wafer by a photo-etching technique atuning fork shaped crystal element having a protrusion ridge linesection that has remained in the lengthwise direction of the +X face ofthe crystal after etching, due to etching anisotropy; an electrodematerial formation for forming a metallic film to be processed aselectrodes, on the tuning fork shaped crystal element of the singlecrystal wafer; and an electrode dividing for dividing the metallic filmalong the protrusion ridge line section, and forming the first andsecond sensor electrodes. As a result, the angular velocity sensorelement can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing describing an angular velocity sensor element, beinga first embodiment of the present invention.

FIG. 2 is a drawing describing a manufacturing method of an angularvelocity sensor element, being a second embodiment of the presentinvention.

FIG. 3 is a drawing describing a manufacturing method of an angularvelocity sensor element, being a third embodiment of the presentinvention.

FIG. 4 is a drawing describing a manufacturing method of an angularvelocity sensor element, being the third embodiment of the presentinvention.

FIG. 5 is a drawing describing a manufacturing method of an angularvelocity sensor element, being another specific example of the thirdembodiment of the present invention.

FIG. 6 is a drawing describing an angular velocity sensor element of aconventional example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As a best mode for implementing an angular velocity sensor element ofthe present embodiment, first and second sensor electrodes are formed bydividing a portion corresponding to a protrusion ridge line section of ametallic film provided on a +X face of a tuning fork shaped crystalelement, along the protrusion ridge line section. As a result, theangular velocity sensor element of the present invention can beconstructed, with formation of the first and second sensor electrodesmade easy.

First of all, the angular velocity sensor element of the presentinvention is constructed by performing division of the metallic filmprovided on the +X face for forming the first and second sensorelectrodes, with a photo-etching technique or a laser technique. Withthese techniques, the angular velocity sensor element of the presentinvention can be easily constructed, ensuring the division of the metalfilm provided on the +X face.

As a best mode for carrying out the manufacturing method of the angularvelocity sensor element of the present invention, here in the electrodedividing step a photo-etching technique is employed, comprising a stepfor forming a positive or negative type photo-resist film on themetallic film of the +X face, a step for removing the photo-resist filmon the protrusion ridge line section by selective exposure anddevelopment appropriate to the positive type or negative type resist,and exposing the metallic film portion, and a step for forming the firstand second sensor electrodes by wet etching the metallic film portion todivide the metallic film. As a result, the metallic film on the +X facecan be reliably divided, and the first and second sensor electrodesobtained.

Furthermore, in the manufacturing method of the angular velocity sensorelement of the present invention, the selective exposure is performedfrom a direction perpendicular to the aforementioned principal plane ofthe crystal wafer. As a result, compared with the conventional methodwhich uses oblique exposure, the equipment itself that is used can besimplified, and problems caused by the oblique exposure such asdifficulty in maintaining accuracy when tilting the wafer stage or lightsource, or difficulty in designing a photo-mask on the assumption ofoblique exposure, can be overcome.

Moreover, the metallic film is formed simultaneously on both principalplanes and each side face by vapor deposition or sputtering, and theelectrodes on the principal planes and the electrodes on the variousside faces including the first and second sensor electrodes (for examplethe electrodes described in FIG. 6A and FIG. 6B denoted by 3 a, 3 b, 4a, 4 b, 5, 6 a, 6 b, 7 a and 7 b), are formed integrally byphoto-etching. As a result it becomes possible to perform division ofthe metallic film which forms the first and second sensor electrodes,and formation of the other electrodes on the principal planes and theside faces simultaneously.

Furthermore, the electrode dividing step involves a laser dividing stepwhich removes by laser, the metallic film portion of the metallic film,which is provided on the protrusion ridge line section. As a result, themetallic film on the +X face is reliably divided, and the first andsecond sensor electrodes are obtained. Here in the method of executingsensor electrode division by laser radiation, equipment cost iscomparatively inexpensive compared with the case where this is done by aphoto-etching technique.

Moreover, the laser division process is executed after the metal filmhas been formed on the principal planes and each side face of the tuningfork arms by vapor deposition or sputtering, and the electrodes of theprincipal planes have been formed by a photo-etching technique. As aresult the step for forming the metallic film, and the time for dividingare well defined.

The laser division process is executed after the electrodes have beenformed on the principal planes by a photo-etching technique, and afterthe metal film has been formed on each side face by a lift-offtechnique. As a result, the electrodes of the principal planes and theside faces can be made from different materials. If the metallic film onthe side faces is formed by a lift-off technique, then compared with thecase where a metallic film is formed on all sides, and then resist isapplied to this and the electrodes are formed by exposing and developingthis resist to selectively etch the metallic film, disconnection at theridge line can be prevented.

Furthermore, the electrodes of both principal planes and the metallicfilm of each side face are made different materials. As a result, forexample the electrodes of the principal planes can be composed of Au(gold) in view of their connecting with the external circuit, while themetallic film of the side faces (electrodes) can be made from Ag(silver) which has a smaller mass than Au. As a result, degradation ofcrystal-impedance and the like caused by mass loading can be prevented.

Also in the present invention, when formation of the side faceelectrodes is executed by a lift-off technique, Ag can be used as theelectrode material. Therefore compared to the case where Au (gold) isused, a production effect can also be obtained where metallic burrs areunlikely to occur after lift-off. Furthermore, since the etchingselection ratio of Au and Ag is easily achieved, it is fully possible toregenerate the side face electrodes if a defect occurs in theirformation.

First Embodiment

FIG. 1 is a drawing describing one embodiment of an angular velocitysensor element of the present invention, FIG. 1A being a perspectiveview and FIG. 1B being a plan view of the tuning fork arms viewed fromabove.

The angular velocity sensor element of the present invention comprises atuning fork shaped crystal element 10. Driving electrodes 3 a, 3 b, 4 a,and 4 b are formed on the front, back, inside and outside side faces ofone tuning fork arm 1 a extending from a tuning fork base portion 2, anda ground electrode 5 and a pair of first and second sensor electrodes 6a and 6 b are formed on the inside and outside side faces of the othertuning fork arm 1 b, and monitor electrodes 7 a and 7 b are formed onboth principal planes. The driving electrodes 3 a, 3 b, 4 a, and 4 b,the monitor electrodes 7 a and 7 b, the ground electrode 5, and thesensor electrodes 6 a and 6 b are connected as shown in FIG. 6Bmentioned above.

Moreover, the tuning-fork shaped crystal element 10 is formed from asingle plate crystal wafer (not shown in the drawing) by a photo-etchingtechnique, that is, a photolithography technique and a wet etchingtechnique. In this case, due to the etching anisotropy of the crystal,after etching, a peak shaped protrusion, that is, a protrusion ridgeline section 8 is formed along the lengthwise direction of the tuningfork arm on the side face corresponding to the +X face of the crystal,among the side faces of each of the tuning fork arms 1 a and 1 b, andboth sides of the ridge line section become inclines.

The right side face when the tuning fork shaped crystal element 10 isseen in an erect state is the +X face of the crystal. Also, theprotrusion ridge line section 8 denotes a region having a spread in thewidthwise direction of the tuning-fork, and includes part of both theside inclined faces of the protrusion ridge line section 8 that occur onthe +X face.

Moreover the electrodes of both principal planes (front and back face)of each tuning fork arm 1 a and 1 b, and each side face, are formed by aphoto-etching technique. Furthermore, here, with the protrusion ridgeline section 8 formed on the outside side face of the other tuning forkarm 1 b as a dividing region, the first and second sensor electrodes 6 aand 6 b are formed on the inclined faces on both sides thereof.

In the embodiment shown in FIG. 1A and FIG. 1B, the electrode dividingsection is provided centered on the protrusion ridge line section 8 sothat both sides thereof become substantially even. However, theelectrode dividing section may be formed from the apex of the protrusionridge line section to only one principal plane side of the tuning fork.In short, the dividing section of the sensor electrodes 6 a and 6 b onlyhas to be formed by actively using the protrusion occurring on the +Xface, and an inclined surface from the protrusion towards the tuningfork principal plane.

Moreover, in this embodiment, driving electrodes 3 a provided on thefront and back face of the one tuning fork arm 1 a are commonlyconnected with a wiring pattern 9 a provided on the inclined face of the+X face. Also, a wiring pattern 9 b of a second sensor electrode 6 bprovided on the other tuning fork arm 1 b extends to the front face overthe protrusion ridge line section 8 and across the inclined face. Hereother wiring patterns are omitted. Of course the connection exampleshown here is one example, and other connection methods may be used

According to such a construction, in the angular velocity sensor elementof the present invention, the first and second sensor electrodes 6 a and6 b are formed here on the outside face, “+X face”, of the other tuningfork arm 1 b of the tuning fork shaped crystal element 10, and arearranged on both sides of the protrusion ridge line section. As aresult, as is later described in a second and third embodiment, afterthe metallic film is formed over the whole side face (X face) of thetuning fork shaped crystal element 10, if the metallic film portion onthe protrusion ridge line section is removed to divide this, by aphoto-etching or laser technique or the like, the first and secondsensor electrodes 6 a and 6 b can be easily obtained.

Moreover, in the angular velocity sensor element of the presentinvention, the protrusion section and the inclined face formed on the +Xface are used. Therefore, particularly when dividing the metallic filmusing the photo-etching technique or the laser technique (irradiation),exposure or laser irradiation to the single crystal wafer only needs tobe executed from the perpendicular direction. As a result, an increasein the size and complexity of the equipment used can be avoided, andsimplification is possible.

Also, basically in the present invention, the formation of theelectrodes employs a photo-etching technique (photolithography) andlaser irradiation technique. Therefore the position and area of theelectrodes formed on the principal planes and the side faces, includingthe first and second sensor electrodes 6 a and 6 b , can be controlledwith a high degree of accuracy.

Furthermore, both sides of the protrusion ridge line section on whichthe first and second sensor electrodes 6 a and 6 b are formed areinclined faces. Therefore the electrode area can be made greater anddetection sensitivity can be improved compared to the case of ahorizontal surface. The effect of this becomes significant asminiaturization of the sensor element progresses.

Moreover, in the first embodiment, the driving electrodes 3 a and 3 bprovided on the front and back face of the one tuning fork arm 1 a arecommonly connected by the wiring pattern 9 a provided on the inclinedface of the +X face. Similarly, the wiring pattern 9 b of the secondsensor electrode 6 b provided on the other tuning fork arm 1 b alsoextends across the inclined face to the front face. Consequently,disconnection can be prevented compared to the case where the wiringpattern is provided on a right-angled face.

Second Embodiment

FIG. 2 is a drawing describing a manufacturing method of the angularvelocity sensor element of the first embodiment of the presentinvention, FIG. 2A being a partial plan view of the single crystalwafer, FIG. 2B being a plan view of an angular velocity sensor elementshowing the exposure condition, and FIG. 2C being a plan view afterexposure.

The manufacturing method of an angular velocity sensor element of thepresent invention comprises, in order of time, an outline processingstep, an electrode material forming step, and an electrode dividingstep.

First of all, in the outline processing step, a plurality of tuning forkshaped crystal elements 10 are formed on a Z-cut single crystal wafer 11by a photo-etching technique (photolithography technique and wet etchingtechnique).

In this case, the etching condition is controlled so that the protrusionridge line section 8 formed along the lengthwise direction due to theetching anisotropy of the crystal as described above, remains and isformed on the +X face, among the side faces of the tuning fork shapedcrystal element 10. A number of tuning fork shaped crystal elements 10are integrated for example by having part of their base bottom facesconnected to a frame. Here too, the +X face of the crystal is the rightside when viewing the tuning fork shaped crystal elements 10 in theupright condition (see FIG. 2A).

Next, in the electrode material forming step, a metallic film 12 servingas the electrode material is formed on each side face (inside andoutside side faces) including both principal planes and the +X face ofeach tuning fork shaped crystal element 10 formed on the single crystalwafer 11. In the metallic film 12, for example, a first layer (substrateelectrode) is Cr, and a second layer is Au. These layers are formedsimultaneously on both principal planes and each side face by vapordeposition or sputtering.

Finally, in the electrode division step, the metallic film on the +Xface, being the outside side face of the tuning fork shaped crystalelement 10, is divided along the protrusion ridge line section 8 to formthe first and second sensor electrodes 6 a and 6 b . This is performedwith a photo-etching technique, and the electrodes on each side face,including the principal planes and the +X face, are formedsimultaneously.

More specifically, first of all a resist film 13 is formed on themetallic film 12 provided on both principal planes and each side face ofthe tuning fork shaped crystal element 10. For this resist film 13, bothpositive type and the negative type resist are acceptable. Here, anexample using a positive type resist is shown.

Next, photomasks 14 are arranged on both principal plane sides of thesingle crystal wafer 11 that has the tuning fork shaped crystal elements10. In the photomask 14, a light shielding pattern 14 b that correspondsto a resist pattern needed for the electrode formation, is formed on alight transmission body 14 a such as silica glass. Then, light isirradiated onto the photomasks 14 of both principal planes, from theperpendicular direction (frontal direction) as shown by the arrows (seeFIG. 2B).

In this case, it is particularly important to irradiate light to theresist film on the portion on the protrusion ridge line section 8, thatcorresponds to the dividing region of the first and second sensorelectrodes 6 a and 6 b. As a result, the portions of the resist film 13,that are unnecessary for the electrode pattern including the sensorelectrode dividing region of the +X face, are exposed, and the portionsthat are necessary for forming the electrode pattern are light shielded(so-called “selective exposure”).

Next, after being selectively exposed, the single crystal wafer 11 isprocessed with developer to dissolve the unnecessary parts of the resistfilm 13. As a result, a resist pattern corresponding to the electrodeson the principal planes and the electrodes on the side faces, includingthe sensor electrodes 6 a and 6 b on the +X face, is formed on themetallic film 12. Therefore, the metallic film portion that is notnecessary for forming electrodes on the principal planes and on the sidefaces, including the protrusion ridge line section 8 between the sensorelectrodes 6 a and 6 b on the +X face, can be exposed (see FIG. 2C). Themetallic film 12 and the resist film 13 on the tuning fork base portion2 are omitted in this drawing.

Next, the developed single crystal wafer 11 is immersed in the etchantfor the metallic film 12. As a result, the unnecessary electrode filmportion is removed, and the electrodes on each side face and theprincipal planes, including the sensor electrodes 6 a and 6 b on the +Xface formed on both sides of the protrusion ridge line section 8, can beobtained (see FIG. 1B). FIG. 1B shows the condition where the resistfilm on each electrode has been removed.

According to such a manufacturing method of an angular velocity sensorelement of the present invention, as previously mentioned, the first andsecond sensor electrodes 6 a and 6 b can easily be formed on the sideface, being the outside face of the tuning fork arm 1 b, correspondingto the +X face of the crystal. Moreover, in the present invention, sinceformation of the electrodes employs a photolithography technique, theposition and area thereof can basically be controlled with a high degreeof accuracy.

More specifically, the position and the area can be controlled with ahigh degree of accuracy compared to the mechanical type that uses aplating frame and the like, and light only has to be irradiated from thedirection perpendicular to the protrusion ridge line section 8, comparedto with photo-etching in which light is irradiated from an obliquedirection. Therefore the equipment used need not be large, and theaforementioned problem of oblique exposure can be overcome.

Furthermore, in the first embodiment, the driving electrodes 3 a and 3 bprovided on the front and back face of the one tuning fork arm 1 a arecommonly connected by the wiring pattern 9 a provided on the inclinedface of the +X face. Similarly, the wiring pattern 9 b of the secondsensor electrode 6 b provided on the other tuning fork arm 1 b alsoextends across the inclined face to the front face. Consequently,disconnection can be prevented compared to the case where the wiringpattern is provided on a right-angled face.

Moreover, the first and second sensor electrodes 6 a and 6 b arerespectively formed on the inclined surfaces on both sides of theprotrusion ridge line section 8 of the other tuning fork arm 1 b.Consequently, the area of these inclined surfaces is greater than in thecase where the side face is a flat surface. Therefore the electrode areacan be formed large. As a result, the amount of electric charge due tothe Coriolis force that can be detected can be increased, and hence theangular velocity detection sensitivity is improved.

Third Embodiment

FIG. 3 is a drawing describing a third embodiment of a manufacturingmethod of an angular velocity sensor element of the present invention,being an example of dividing the first and second sensor electrodesusing a laser.

As with the first embodiment described above, the third embodiment alsocomprises an outline processing step, an electrode material formingstep, and an electrode dividing step. In the third embodiment, theoutline processing step is identical to that of the first embodiment,and the tuning fork shaped crystal element 10 having the protrusionridge line section 8 on the +X face, among the side faces, is formed onthe single crystal wafer 11 by a photo-etching technique (see FIG. 2A).

Next, in the electrode material forming step, similarly to before, themetallic film 12 is formed, having electrode material made of Au and asubstrate of Cr, on each side face, including both principal planes andthe inside faces, of each of the tuning fork shaped crystal elements 10(in short, all faces except for the top and bottom faces). Then themetallic film 12 on both principal planes and each side face isprocessed with a photo-etching technique.

That is to say, in the third embodiment, the electrodes on bothprincipal planes and the electrodes on each side face except for thefirst and second sensor electrodes 6 a and 6 b on the outside face “+Xface” of the tuning fork arm 1 b are formed by a photo-etchingtechnique. In short, the metallic film 12 of the outside face is leftremaining over the entire face (see FIG. 3).

Then, the first and second sensor electrodes 6 a and 6 b are formed onthe plate face of each of the tuning fork shaped crystal elements 10 byirradiating a laser from, for example, the perpendicular direction ontothe protrusion ridge line section 8 of the outside face “+X face”, andremoving the metallic film 12 of the protrusion ridge line section 8. Asa result, the electrodes can be obtained on the principal planes andeach side face (see FIG. 1B). However, as shown in FIG. 4, only theinclined surface on one principal plane side of the protrusion ridgeline section 8 is removed

Also with such a manufacturing method, an effect similar to that of thefirst embodiment of the present invention is achieved, and sincebasically this involves electrode formation using a photolithographytechnique, the position and area can be controlled with a high degree ofaccuracy compared to a mechanical type that uses a plating frame. Also,in the case of using a laser, compared to the exposure executed in thefirst embodiment, irradiation only has to be performed in spots with alaser gun for example. Therefore irradiation not only from theperpendicular direction to the plate face but also from an obliquedirection is acceptable.

In the third embodiment, the electrode material forming step may beperformed as shown in FIG. 5A, FIG. 5B and FIG. 5C differently to theabove description. FIG. 5 is a top view of the other tuning fork arm 1b, and is taken as an example for the description. That is to say, inthe electrode material forming step here, first of all, a tuning forkshaped metallic film (for example Cr+Au) is formed on the front and backsides of a wafer by a photo-etching technique. This wafer is thenimmersed in crystal etchant to obtain a wafer that has a large number oftuning fork parts. Next, the metallic film, which has been used as amask for the crystal etching, is processed with a photo-etchingtechnique to form the electrodes 3 a, 3 b , 7 a, and 7 b on theprincipal planes of the tuning fork. Here, an example of the right armonly, that is, an example with monitor electrodes 7 a and 7 b formed isshown (see FIG. 5A). Next, the resist pattern 13 is formed so that theresist remains in the region apart from the region in which the sideface electrodes will be formed.

Next the metallic film 12 is formed on all faces including bothprincipal planes and each side face (see also FIG. 5B). Then, themetallic film 12 is provided on each side face by a so-called lift-offtechnique, in which the metallic film 12 on the principal planes of thetuning fork is removed by chemically releasing the resist film 13 (seeFIG. 5C). The metallic film on the inside face becomes a groundelectrode 5 as is. Moreover, similarly to as described above, the firstand second sensor electrodes 6 a and 6 b can be formed by irradiating alaser onto the protrusion ridge line section 8 (see FIG. 1B).

In this case, an effect similar to that mentioned above can be achieved,and the metallic film 12 on the side faces can be separately selectedfrom the metal on the principal planes. Here, by selecting silver forexample, the dividing operation by means of lift-off or laser isfacilitated. That is to say, since silver is less malleable than gold,an effect can also be achieved in that hair-like metal shavings are notproduced, and the cleaning process becomes unnecessary. Furthermore, theequipment can be simplified and man-hours reduced since Ag can beremoved with a lower energy laser compared to Au.

In the embodiments described above the first and second sensorelectrodes 6 a and 6 b are provided on the outside face of the othertuning fork arm lb. However, they may be provided on the inside face ofthe one tuning fork arm 1 a. In this case, the driving electrode 4becomes on the other tuning fork arm 1 b. Moreover the driving electrode4 is formed on the one tuning fork arm 1 a, and the sensor electrodes 6a and 6 b are formed on the other tuning fork arm 1 b. However they maybe provided on both +X faces of the pair of tuning fork arms 1 a and 1 bdepending on the driving method and the like. However, providing thesensor electrodes 6 a and 6 b on the other tuning fork arm 1 b andmaking the one tuning fork arm 1 a a dedicated arm for tuning forkvibration enables electrode positioning to be simple. Moreover, problemsof the tuning fork drive signal influencing the sensor electrodes 6 aand 6 b via capacitive coupling between the driving electrode and thesensor electrode can be easily reduced.

1. A tuning fork type crystal component for an angular velocity sensorcomprising: a tuning fork shaped crystal element having a pair of tuningfork arms extending from a tuning fork base portion where an X axis of acrystal axis (XYZ) is a widthwise direction, a Y axis is a lengthwisedirection and a Z axis is a depthwise direction; and mutuallyelectrically separated first and second sensor electrodes for angularvelocity detection formed on at least one face among side faces of saidtuning fork arms; wherein said tuning fork shaped crystal element isformed by a photo-etching technique, and said first and second sensorelectrodes are formed on a +X face among the side faces of said tuningfork arms, and are arranged on both sides of a protrusion ridge linesection formed in a lengthwise direction of said +X face due tocrystallinity of said crystal.
 2. A tuning fork type crystal componentfor an angular velocity sensor according to claim 1, wherein said firstand second sensor electrodes are formed by dividing along saidprotrusion ridge line section, a portion of a metallic film provided onsaid +X face of said tuning fork shaped crystal element, correspondingto an apex of said protrusion ridge line section.
 3. A tuning fork typecrystal component for an angular velocity sensor according to claim 2,wherein said dividing is performed by a photo-etching technique.
 4. Atuning fork type crystal component for an angular velocity sensoraccording to claim 2, wherein said dividing is performed by a lasertechnique.